Thyroid Flashcards
What is the name of an enlarged thyroid gland?
Goiter.
Describe the structure of the thyroid gland.
There are areas called colloid which are surrounded by simple cuboidal epithelial cells called follicular cells. The basolateral membrane is on the side outside of the colloid. The other membrane is the apical membrane.
What is the function of the thyroid gland?
Its main function is to synthesise and secrete Thyroid Hormone.
What precursor molecule is a major constituent of thyroid follicle?
Thyroglobulin.
What can be said about the blood supply in the thyroid gland?
It is very large and comes from both inferior and superior thyroid arteries.
What is the effect of the sympathetic nervous system on the thyroid gland?
This increases secretion of thyroid hormones.
What is the effect of TRH on the pituitary gland?
TRH binds to receptors and this increases calcium which causes exocytosis of TSH.
Where in the thyroid gland does TSH bind?
It binds to the basolateral membrane of the follicular cells.
Name three things which activation of a TSH receptor leads to.
Iodine uptake, production of Idothyrines, promotion of thyroid growth.
What does chronically high TSH lead to?
This stimulates thyroid growth and division of follicular cells leading to an enlarged gland.
Where is iodine for thyroid hormone synthesis derived from?
The diet.
What enzyme activates iodine so that it can combine with thyroglobulin?
Perioxidase enzyme.
Where is thyroglobulin produced?
This is produced by ribosomes in the follicular cells. It is then transported through the Golgi where it is glycosylated and packaged into vesicles before it is stored in the colloid.
What are thyroid hormones synthesised from?
Tyrosine residues on thyroglobulin.
What two substances do thyroid hormones bind to for transport in the blood?
Thyronine binding globulin (TBG) and also to albumin or pre albumin.